The Mk 27 Mod 0, it was classified as a ground, magnetic induction mine -
torpedo shaped. It was 20 feet, 5 and 7/8 inches long and had an optimum
diameter of 21 inches +/- .015 inches to fit the then standard 21 inch torpedo
tubes. Weight empty (less battery) was 1410 lbs. Explosive charge was 854 lbs
HBX-1. Assembled weight was 2620 lbs. It ran at a negative buoyancy of 50 lbs.
(when fired) and at the end of the prescribed run flooded with a negative
buoyancy of 1235 lbs.. Case material was steel. It used the
M9-1 firing mechanism, which was a two look reversal (opposite polarity) type
using many relays, resistors, capacitors, etc. (it was one of my favorites for
debugging). It was planted in 4-23 fathoms against surface craft and up to 50
fathoms for submarine targets. Max launching depth was 125 feet at max 10 knots
from forward tubes. Safety features included the extender, run impeller, clock
assembly and Sedarpet Relay. There were two operational assemblies depending on
use of either the CD-10 or the CD-12. Sterilization feature was provided by the
SD-4.
The mine assembly publication was OP 685. The afterbody consisted of the
propeller, main motor, distance setting gear, gyro (control of run 0-60
degrees), depth setting device, depth bellows and pendulum for the depth control
setting, and starting gear. The battery (war) compartment contained the battery
discharge resistor, battery charger receptacle, priming switch (max 15
minutes-minimum 2), batteries (2 sections of 24 and 75 volts), flood valves,
explosive charge, booster and detonator, Mk 14 extender (lock-ball type),
sterilizer (8.5-350 days), ships counter (TB-10), sensitivity switch, clock
delay CD-10/CD-12, clock starter (lock-ball type). The nose section
contained the firing mechanism and impeller.
Curtsey of Toby Horn CDR RET.